Intersexual 'arms race' and the evolution of the sphragis in Pteronymia butterflies

Sexual reproduction is often associated with intra- and intersexual conflict, especially in species where females mate multiple times. A strategy that has evolved in males to ensure offspring paternity is the ability to produce a complex, external mating plug called a sphragis. The sphragis has been found in 273 butterfly species; however, little is known about the sphragides of the butterflies in the nymphalid genus Pteronymia. In this study, we describe the sphragides of all sphragis-bearing species in Pteronymia, including the newly discovered sphragides of P. alissa (Hewitson), P. andreas (Weeks), P. ozia (Hewitson), and P. zerlina (Hewitson). Three additional species, P. fulvimargo Butler & Druce, P. oneida (Hewitson), and P. ticida (Hewitson), are found to bear an irregular sphragis-like structure. We use molecular and morphological data from a recent study to construct a phylogeny of species in the genus and examine the number of independent origins of the sphragis. Our ances...